arXiv subjects

Vivi Petersen

Publications and source records attributed to Vivi Petersen.

3 recordsLinked to original sources

arXiv2006

Estimation of fluctuating magnetic fields by an atomic magnetometer

We present a theoretical analysis of the ability of atomic magnetometers to estimate a fluctuating magnetic field. Our analysis makes use of a Gaussian state description of the atoms and the probing field, and it presents the estimator of the field and a measure of its uncertainty which coincides in the appropriate limit with the achievements for a static field. We show by simulations that the estimator for the current value of the field systematically lags behind the actual value of the field, and we suggest a more complete theory, where measurement results at any time are used to update and improve both the estimate of the current value and the estimate of past values of the B-field.

quant-ph↗

arXiv2005

Gaussian State Description of Squeezed Light

We present a Gaussian state description of squeezed light generated in an optical parametric oscillator. Using the Gaussian state description we describe the dynamics of the system conditioned on homodyne detection on the output field. Our theory shows that the output field is squeezed only if observed for long enough times or by a detector with finite bandwidth. As an application of the present approach we consider the use of finite bandwidth squeezed light together with a sample of spin-polarized atoms to estimate a magnetic field.

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arXiv2004

Magnetometry with entangled atomic samples

We present a theory for the estimation of a scalar or a vector magnetic field by its influence on an ensemble of trapped spin polarized atoms. The atoms interact off-resonantly with a continuous laser field, and the measurement of the polarization rotation of the probe light, induced by the dispersive atom-light coupling, leads to spin-squeezing of the atomic sample which enables an estimate of the magnetic field which is more precise than that expected from standard counting statistics. For polarized light and polarized atoms, a description of the non-classical components of the collective spin angular momentum for the atoms and the collective Stokes vectors of the light-field in terms of effective gaussian position and momentum variables is practically exact. The gaussian formalism describes the dynamics of the system very effectively and accounts explicitly for the back-action on the atoms due to measurement and for the estimate of the magnetic field. Multi-component magnetic fields are estimated by the measurement of suitably chosen atomic observables and precision and efficiency is gained by dividing the atomic gas in two or more samples which are entangled by the dispersive atom-light interaction.

quant-ph↗